This question was asked inGPSC Deputy Executive Engineer (Electrical) Class-2 Master Paper 2026Question 43 of 195 published · Gujarat Public Service CommissionOpen paper
Q43ModerateVector Calculus

सदिश कलन (vector calculus) के संबंध में निम्नलिखित कथनों पर विचार कीजिए:
1. किसी सदिश क्षेत्र का अपसरण (divergence) किसी बिंदु से प्रति इकाई आयतन शुद्ध बाहरी फ्लक्स को दर्शाता है और स्रोत या सिंक की उपस्थिति बताता है।
2. किसी सदिश क्षेत्र का कर्ल क्षेत्र की घूर्णी प्रवृत्ति मापता है और संरक्षी (conservative) क्षेत्रों के लिए शून्य होता है।
3. किसी अदिश क्षेत्र का ग्रेडिएंट हमेशा परिवर्तन की दर दर्शाने वाली अदिश राशि देता है।
4. अपसरण प्रमेय बंद सतह पर सदिश क्षेत्र के पृष्ठ समाकल को अपसरण के आयतन समाकल से जोड़ता है।
उपरोक्त में से कौन-सा/से कथन सही है/हैं?

उत्तर और चरणबद्ध हल
सही उत्तर: A. केवल 1, 2 और 4
संक्षिप्त व्याख्या

तीनों मूल सदिश अवकल संकारकों के आउटपुट अलग हैं: ग्रेडिएंट अदिश→सदिश, अपसरण सदिश→अदिश, और कर्ल सदिश→सदिश। ग्रेडिएंट सदिश देता है, इसलिए कथन 3 गलत है; सही उत्तर 1, 2 और 4। सूत्र: ∮_S A·dS = ∫_V (∇·A)dV।

विस्तृत हल (मूल भाषा में)

Statement-wise Verification

  • Statement 1 - Correct.
    The divergence of a vector field represents the net outward flux per unit volume from a point and indicates the presence of sources or sinks.
    Divergence is a scalar measuring net outward flux density/source strength at a point.
  • Statement 2 - Correct.
    The curl of a vector field measures the rotational tendency of the field and is zero for conservative fields.
    Curl is a vector measuring local rotational tendency; for a sufficiently smooth conservative field F=−∇V, ∇×F=0.
  • Statement 3 - Incorrect.
    The gradient of a scalar field always results in a scalar quantity representing rate of change.
    ∇φ is a vector field pointing in the direction of steepest increase of scalar φ.
  • Statement 4 - Correct.
    Divergence theorem relates surface integral of a vector field over a closed surface to volume integral of divergence.
    The divergence theorem converts closed-surface flux into a volume integral of divergence.

Core Concept

The three basic vector differential operators have distinct outputs: gradient maps scalar→vector, divergence maps vector→scalar, and curl maps vector→vector. Remembering input/output type is often enough to eliminate distractors.

Formula / Key Relationship

grad φ=∇φ; div A=∇·A; curl A=∇×A; ∮_S A·dS = ∫_V (∇·A)dV.

Step-by-Step Check

Type-checking immediately disproves statement 3. The geometric meanings and divergence theorem confirm 1, 2 and 4, yielding A.

Why the Other Options Are Wrong

Option B is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 2, 4. Option C is incorrect because it includes incorrect statement(s) 3 and omits correct statement(s) 1, 4. Option D is incorrect because it includes incorrect statement(s) 3.

Answer-Key Verification Note

The uploaded provisional key marks C . After independent technical verification, the defensible answer is A . This discrepancy is stated explicitly rather than silently copying the provisional key.

Exam Shortcut / Approach

Use the mnemonic: Grad grows a scalar into a vector; Div gives a scalar; Curl gives a vector.

Common Mistake

Calling gradient a scalar because the original field is scalar.

Quick Revision

Vector Differential Operators is linked with Gradient Divergence and Curl, Vector Calculus and Electromagnetic Fields. Use the mnemonic: Grad grows a scalar into a vector; Div gives a scalar; Curl gives a vector.

Verified · SRO editorial desk Report
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